CVE-2026-42085 | OpenC3 COSMOS: Arbitrary write to plugins directory via path-traversed config filenames

Exp

OpenC3 COSMOS provides the functionality needed to send commands to and receive data from one or more embedded systems. Prior to versions 6.10.5 and 7.0.0-rc3, OpenC3 COSMOS contains a design flaw in the save_tool_config() function that allows saving tool configuration files at arbitrary locations inside the shared /plugins directory tree by supplying crafted configuration filenames. Although the implementation sufficiently mitigates standard path traversal attacks, by canonicalizing filename to an absolute path, all plugins share this same root directory. That enables users to create arbitrary file structures and overwrite existing configuration files within the shared /plugins directory. This issue has been patched in versions 6.10.5 and 7.0.0-rc3.

Published: 2026-05-04 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-42085 is rated Exploit Available (50/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.31%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2026-42085

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2026-42085

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.06% 0.31% +0.26%
2 2026-06-05 0.04% 0.06% +0.02%
3 2026-05-05 — 0.04% —

Full EPSS history (3 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-42085

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
4.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 1.4 [email protected]

Weakness enumeration for CVE-2026-42085

GitHub Security Advisory for CVE-2026-42085

GHSA-4jvx-93h3-f45h · Severity: medium · Ecosystem: rubygems — OpenC3 COSMOS allows arbitrary writes to plugins directory via path-traversed config filenames

Affected software / configurations for CVE-2026-42085

Vendor Product Version Raw CPE
openc3 cosmos < 6.10.5 cpe:2.3:a:openc3:cosmos:*:*:*:*:open_source:*:*:*
openc3 cosmos 7.0.0 cpe:2.3:a:openc3:cosmos:7.0.0:rc1:*:*:open_source:*:*:*
openc3 cosmos 7.0.0 cpe:2.3:a:openc3:cosmos:7.0.0:rc2:*:*:open_source:*:*:*

References for CVE-2026-42085

cvelogic Threat Intelligence